quine (idea)

[from the name of the logician Willard
van Orman Quine, via Douglas Hofstadter] A program that generates a
copy of its own source text as its complete output. Devising the
shortest possible quine in some given programming language is a
common hackish amusement. (We ignore some variants of BASIC
in which a program consisting of a single empty string literal
reproduces itself trivially.) Here is one classic quine:

This one works in LISP or Scheme. It's relatively easy to write
quines in other languages such as Postscript which readily handle
programs as data; much harder (and thus more challenging!) in
languages like C which do not. Here is a classic C quine for ASCII
machines: